Method for surface-coating synthetic resins

ABSTRACT

A surface protective coating layer being excellent in weather resistance and chemical resistance is formed on a synthetic resin substrate. An aqueous dispersion of fluorine-containing resin is applied to the synthetic resin substrate.

TECHNICAL FIELD

The present invention relates to a method of applying, to a syntheticresin substrate, a surface protective coating which is excellent inweather resistance and chemical resistance.

BACKGROUND ART

Hitherto a range of use of general-purpose resins such as vinyl chlorideresin, vinyl acetate resin and acrylic resin and in addition,engineering plastics such as nylon, polyacetal, polycarbonate, modifiedPPO resin and modified PBT resin has been increasing in various fieldsbecause they have excellent heat resistance and impact resistance. Forimprovement in light stability and solvent resistance (solvent cracking)thereof, coating with a fluorine-containing resin has been desired.

As the method of such coating, a solvent-coating method of coating afluorine-containing resin dissolved in a specific solvent has beenproposed (JP-A-63-199771). However since a solvent is used, the methodis disadvantageous from the viewpoint of removal of solvent, cost forrecovering a solvent and working environment such as safety. In view ofimprovement of those properties, development of an aqueous coatingmethod has been desired.

When a synthetic resin substrate contacts a solvent, deterioration ofits surface arises. In order to prevent the surface deterioration, therehas been proposed a method of coating by using a solvent having a lowsolubility such as a non-polar solvent or an alcoholic solvent. Howeverin that method, sufficient adhesion to the resin substrate cannot beobtained.

The present invention can provide a method of forming a surfaceprotective coating of a fluorine-containing resin on a surface ofsynthetic resin, in which the above-mentioned problems can be eliminatedby applying the fluorine-containing resin composition in the form of anaqueous dispersion and then drying.

DISCLOSURE OF THE INVENTION

The present invention provides a method of forming, on a syntheticresin, a surface protective coating layer being excellent in weatherresistance and chemical resistance by applying an aqueous dispersion offluorine-containing resin to a surface of the synthetic resin.

Also the present invention provides a transparent laminated article ofsynthetic resin which is obtained by the above-mentioned method. Furtherit is preferable that the fluorine-containing resin in the aqueousdispersion has at least one functional group selected from the groupconsisting of hydroxyl, epoxy and carboxyl.

In the present invention, an aqueous dispersion of fluorine-containingresin is an aqueous dispersion in which the fluorine-containing resinparticles are stably dispersed in water. Such an aqueous dispersion offluorine-containing resin itself is a known one (for example,JP-A-8-120210, JP-A-8-120211, JP-A-4-7784, JP-A-7-258499).

BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the fluorine-containing resin particles used for the aqueousdispersion of fluorine-containing resin of the present invention areparticles of (1) a fluoroolefin polymer, (2) a copolymer of fluoroolefinand monomer copolymerizable therewith and (3) a composite resincomprising a non-fluorine-containing resin and the above-mentionedpolymer or copolymer.

Examples of fluoroolefin are, for instance, fluoroolefins having 2 to 4carbon atoms such as vinyl fluoride, vinylidene fluoride (VdF),tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE),hexafluoropropylene (HFP) and trifluoroethylene.

Examples of the fluoroolefin polymer (1) are homopolymers of thosefluoroolefins or copolymers comprising two or more of thosefluoroolefins. Examples thereof are homopolymers of VdF, TFE and CTFE,VdF/TFE copolymer, VdF/HFP copolymer, VdF/CTFE copolymer, VdF/TFE/CTFEcopolymer, VdF/TFE/HFP copolymer, TFE/HFP copolymer, and the like.

An aqueous dispersion of particles of fluoroolefin polymer (1) can beprepared through usual emulsion polymerization, for example, byemulsion-polymerizing, through usual method, the above-mentionedfluoroolefin in the presence of an emulsifying agent in an amount of notmore than 5% (% by weight, hereinafter the same unless particularlynoted), preferably not more than 1% on the basis of water.

Water used for the emulsion polymerization is preferably de-ionizedwater. Also it is preferable that the emulsifying agent is afluorine-containing surfactant. Further a reactive fluorine-containingemulsifying agent can be used. It is also possible to use a slightamount of non-fluorine-containing nonionic emulsifying agent together.

The fluorine-containing emulsifying agent used in the present inventionis one or a mixture of compounds containing fluorine atoms in theirstructures and having surface activity. For example, there are an acidrepresented by X(CF₂)nCOOH, in which n is an integer of 6 to 20, X is For H, its metal salt, ammonium salt, amine salt or quaternary ammoniumsalt; an acid represented by Y(CH₂CF₂)mCOOH, in which m is an integer of6 to 13, Y is F or Cl, its metal salt, ammonium salt, amine salt orquaternary ammonium salt; and the like. In addition, it is possible touse solely a reactive emulsifying agent disclosed in JP-A-8-67795 and touse the reactive emulsifying agent in combination with theabove-mentioned fluorine-containing emulsifying agent. Also it ispossible to use a non-fluorine-containing nonionic emulsifying agentdisclosed in JP-A-7-90153 together.

Then the copolymer (2) comprising fluoroolefin and monomercopolymerizable therewith is explained below.

Examples of the monomer copolymerizable with fluoroolefin are, forinstance, ethylene; a-olefins such as propylene and isobutylene; vinylethers such as ethyl vinyl ether (EVE), cyclohexyl vinyl ether (CHVE),hydroxybutyl vinyl ether (HBVE), butyl vinyl ether, isobutyl vinylether, methyl vinyl ether and polyoxyethylene vinyl ether; allyl etherssuch as polyoxyethylene allyl ether, ethyl allyl ether and hydroxyethylallyl ether; allyl alcohols such as allyl alcohol, diallyl alcohol andeugenol; vinyl esters such as vinyl acetate, vinyl lactate, vinylbutyrate, vinyl pivalate, vinyl benzoate, and VEOVA9 and VEOVA10 (brandnames of products available from Shell Chemical Co., Ltd.); allyl esterssuch as allyl acetoacetate; ethylenically unsaturated carboxylic acidssuch as itaconic anhydride, succinic anhydride and crotonic acid; andthe like. Particularly ethylene, α-olefins, vinyl ethers, vinyl esters,allyl ethers and allyl esters are preferably used.

Examples of the copolymer (2) comprising fluoroolefin and monomercopolymerizable therewith are TFE/propylene copolymer, TFE/ethylenecopolymer, TFE/vinyl ester copolymers, TFE/vinyl ether copolymers,HFP/vinyl ether copolymers, HFP/vinyl ester copolymers, CTFE/vinyl ethercopolymers, and the like. Further there are copolymers comprising threeor more monomers, i.e. copolymers containing the above-mentionedcopolymer and as a modifying monomer, the above-mentioned monomercopolymerizable with fluoroolefin in an amount of not more than 30% bymole.

It is preferable that the fluoroolefin monomer is contained in thosecopolymers comprising fluoroolefin and monomer copolymerizable therewithin an amount of 20 to 80% by mole.

When an amount of the fluoroolefin monomer is less than 20% by mole,weather resistance cannot be exhibited sufficiently. When more than 80%by mole, it is not preferable because at the time of making a coatingand forming a coating film, lowering of appearance occurs.

The aqueous dispersion of particles of fluoroolefin copolymer (2) can beprepared, for example, through the same emulsion polymerization as inthe preparation of the aqueous dispersion of particles of fluoroolefinpolymer (1).

It is preferable that the copolymer of fluoroolefin and monomercopolymerizable with fluoroolefin has at least one functional groupselected from the group consisting of hydroxyl, epoxy and carboxyl.Examples of a preferred monomer for introducing such a functional groupare, as monomers having hydroxyl, hydroxyl-containing vinyl ethers suchas HBVE; hydroxyl-containing allyl compounds such as allyl alcohol andhydroxyethyl allyl ether; hydroxyl-containing (meth)acrylates such ashydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl(meth)acrylate and polyethylene glycol (meth)acrylate; and the like.Also as a glycidyl-containing monomer for introducing epoxy, there areallyl glycidyl ether, glycidyl (meth)acrylate and the like. As acarboxyl-containing monomer, there are an acrylic acid, methacrylicacid, succinic acid, itaconic acid, crotonic acid, fumaric acid, maleicacid, and the like.

It is preferable that a content of such a functional group-containingmonomer unit in the fluorine-containing resin is from 0.1 to 30% bymole. When less than 0.1% by mole, in some cases, adhesion of afluorine-containing resin to a substrate is insufficient. When more than30% by mole, there is a case where stability of the composition andwater resistance of an obtained coating film are lowered.

Subsequently the composite resin (3) which is one of thefluorine-containing resins used in the present invention is explainedbelow.

Examples of the composite resin comprising the polymer (1) or copolymer(2) and a resin containing no fluorine are a fluorine-containingcomposite resin prepared by seed-polymerizing, in water medium, amonomer having a, radically polymerizable unsaturated bond in thepresence of particles of the fluoroolefin polymer (1) or the copolymer(2) comprising fluoroolefin and monomer copolymerizable therewith, andthe like.

Examples of the monomer having a radically polymerizable unsaturatedbond are alkyl acrylates having alkyl of C1 to C18, alkyl methacrylateshaving alkyl of C1 to C18, a monomer having an ethylenically unsaturatedunit being copolymerizable therewith, and the like.

As the alkyl acrylates having alkyl of C1 to C18, there are, forexample, methyl acrylate, ethyl acrylate, propyl acrylate, n-butylacrylate, isobutyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate andthe like.

As the alkyl methacrylates having alkyl of C1 to C18, there are, forexample, methyl methacrylate, ethyl methacrylate, propyl methacrylate,n-propyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate,lauryl methacrylate and the like.

For the purposes to enhance solvent resistance and water resistance, itis possible to copolymerize a polyfunctional monomer such as ethyleneglycol dimethacrylate and propylene glycol dimethacrylate.

Examples of the monomer which has ethylenically unsaturated unit beingcopolymerizable with the acrylate and/or the methacrylate are, forinstance, ethylene; α-olefins such as propylene and isobutylene; vinylethers such as ethyl vinyl ether (EVE), cyclohexyl vinyl ether (CHVE),hydroxybutyl vinyl ether (HBVE), butyl vinyl ether, isobutyl vinylether, methyl vinyl ether and polyoxyethylene vinyl ether; allyl etherssuch as polyoxyethylene allyl ether, ethyl allyl ether and hydroxyethylallyl ether; allyl alcohols such as allyl alcohol, diallyl alcohol andeugenol; allyl esters such as allyl acetoacetate; vinyl esters such asvinyl acetate, vinyl lactate, vinyl butylate, vinyl pivalate, vinylbenzoate, and VEOVA9 and VEOVA10 (brand names of products available fromShell Chemical Co., Ltd.); ethylenically unsaturated carboxylic acidssuch as itaconic anhydride, succinic anhydride and crotonic acid;aromatic vinyl compounds such as styrene, α-methyl styrene andp-tert-butyl styrene; acrylonitrile; and the like.

Among the polymers (1) and copolymers (2) as the seed particles, fromthe viewpoint of good compatibility with the above-mentioned acrylicmonomer at the time of seed polymerization, VdF fluoroolefin polymer (1)is preferred, and further preferred is the polymer (1) containing a VdFunit in an amount of not less than 50% by mole.

In the present invention, it is preferable that the composite resin (3)contains 20 to 90% by mole of the polymer (1) or the copolymer (2) basedon the whole composite resin (3).

When the fluoroolefin monomer is less than 20% by mole, weatherresistance cannot be exhibited sufficiently, and when more than 90% bymole, it is not preferable because at the time of making a coating andforming a coating film, appearance is lowered.

Also in the present invention, it is preferable, in the seedpolymerization, to use a monomer having at least one functional groupselected from the group consisting of hydroxyl, epoxy and carboxyl tointroduce the functional group in an amount of from 0.1 to 30% by molebased on the whole composite resin (3). As the preferred monomers havinghydroxyl, there are hydroxyl-containing vinyl ethers such as HBVE;hydroxyl-containing allyl compounds such as allyl alcohol andhydroxyethyl ally ether; hydroxyl-containing (meth)acrylates such ashydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl(meth)acrylate and polyethylene glycol (meth)acrylate; and the like.Also as a glycidyl-containing monomer for introducing epoxy, there areallyl glycidyl ether, glycidyl (meth)acrylate, and the like. As acarboxyl-containing monomer, there are (meth)acrylic acids, and thelike.

The seed polymerization of the ethylenically unsaturated monomer can becarried out under the same conditions as in usual emulsionpolymerization. For example, into a water medium containing particles ofthe fluorine-containing polymer (1) or (2) are added a surfactant, apolymerization initiator, a chain transfer agent and as case demands, achelating agent, a pH control agent, a solvent, etc. and then reactionis conducted at about 20° C. to about 80° C. for about 0.5 hours toabout 6 hours.

When the ethylenically unsaturated monomer is emulsion-polymerized inthe presence of particles of the fluorine-containing polymer, it seemsthat at first, there occurs swelling of the particles of thefluorine-containing polymer with the monomer and at that time, themixture becomes in the state of an aqueous dispersion of thefluorine-containing polymer dissolved uniformly in the acrylic monomer,and then the acrylic monomer is polymerized by adding an initiator, toform single phase polymer blend particles, in which the molecular chainsare entangled with each other.

As a surfactant, there is used an anionic surfactant, nonionicsurfactant or combination of the anionic and nonionic surfactants, andas case demands, an amphoteric surfactant can be used.

Examples of the anionic surfactant are a sulfate of higher alcohol,sodium alkylsulfonate, sodium alkylbenzenesulfonate, sodiumdialkylsulfosuccinate, sodium alkyldiphenylether disulfonate, and thelike. Examples of the nonionic surfactant are polyoxyethylene alkylethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkylesters, polyoxyethylene alkyl phenyl esters, sorbitan alkyl esters,glycerol esters, their derivatives, and the like. As the amphotericsurfactant, there are lauryl betaine, and the like.

Further a so-called reactive emulsifying agent which is copolymerizablewith the ethylenically unsaturated monomer can be used. Examples ofcommercially available reactive emulsifying agent are Blemmar PE-350,Blemmar PME-400 and Blemmar 70PEP350B (available from NOF Corporation);NK Ester M-40G, NK Ester M-90G and NK Ester M-230G (available fromShin-Nakamura Kagaku Kabushiki Kaisha); RMA450M (available from NipponNyukazai Kabushiki Kaisha); Aquaron HS10, Aquaron HS20, Aquaron HS1025,Aquaron RN10, Aquaron RN20, Aquaron RN30, Aquaron RN50 and AquaronRN2025 (available from Dai-ichi Kogyo Seiyaku Kabushiki Kaisha); NKEster AMP-60G, NK Ester CB-1, NK Ester SA and NK Ester A-SA (availablefrom Shin-Nakamura Kagaku Kabushiki Kaisha); Eleminol JS2 and EleminolRS30 (available from Sanyo Kasei Kabushiki Kaisha); Latemle WX(available from Kao Corporation); and the like.

An amount of the surfactant is usually from about 0.05 part by weight toabout 5.0 parts by weight on the basis of 100 parts by weight of theethylenically unsaturated monomer.

The initiator is not particularly limited as far as a radical which canbe used for free radical polymerization in water medium is produced at20° to 90° C. As case demands, the initiator can be used in combinationwith a reducing agent. Examples of the water-soluble initiator are apersulfate, hydrogen peroxide, 2,2-azobis(2-amidinopropane)hydrochloride (AJBA) and the like, and examples of the reducing agentare sodium pyrosulfite, sodium hydrogensulfite, sodium L-ascorbate, andthe like. Examples of oil-soluble initiator arediisopropylperoxydicarbonate (IPP), benzoyl peroxide, dibutyl peroxide,azobisisobutyronitrile (AIBN), and the like.

An amount of the initiator is usually from about 0.05 part by weight toabout 2.0 parts by weight on the basis of 100 parts by weight of theethylenically unsaturated monomer.

A polymerization temperature is from 20° to 90° C., preferably from 30°to 70° C.

Examples of the chain transfer agent are a halogenated hydrocarbon (forexample, chloroform, carbon tetrachloride, or the like), mercaptans (forexample, n-dodecyl mercaptan, t-dodecyl mercaptan, or n-octyl mercaptan)and the like. An amount of the chain transfer agent is usually from 0 toabout 5.0 parts by weight on the basis of 100 parts by weight of theethylenically unsaturated monomer.

As the solvent, there may be used methyl ethyl ketone, acetone,trichlorotrifluoroethane, methyl isobutyl ketone, cyclohexanone, ethylacetate, or the like in such a small amount as not lowering workability,safety against disaster, safety in environment and safety in production.By adding the solvent, there is a case where swelling property of themonomer into the seed polymer particles is improved.

The seed polymerization can be carried out by known methods, forexample, a method of charging the whole amount of monomers in one lot ina reaction system in the presence of the seed particles, a method ofcharging a part of the monomers for the reaction and then charging theremaining monomers continuously or dividedly or a method of charging thewhole amount of monomers continuously.

As the aqueous dispersion of fluorine-containing copolymer which is usedfor the seed polymerization, in order to decrease an average particlesize after the seed polymerization to 200 nm or lower, preferable is anaqueous dispersion containing polymer particles having an averageparticle size of not more than 180 nm in a concentration of 30 to 50%and further preferable is an aqueous dispersion containing polymerparticles having an average particle size of not more than 150 nm in aconcentration of 35 to 60%. If the particle size of the resin after theseed polymerization exceeds 200 nm, sedimentation stability of the resincomposition in the aqueous dispersion is lowered, and even if the resincomposition is the same, elevation of a minimum film forming temperatureof the aqueous dispersion of resin composition is resulted.

In the present invention, as described in the explanations of the resins(2) and (3), it is preferable that the fluorine-containing resin hashydroxyl, epoxy and/or carboxyl from the viewpoint of enhancing adhesionto a substrate. In case of other groups, for example, a hydrolyzablesilyl group and amino group, adhesion to a substrate reversely tends tobe lowered.

To the aqueous dispersion of the present invention can be added,depending on purposes, pigments such as inorganic pigment, syntheticpigment and organic pigment, organo silicate, colloidal silica,water-soluble silicate, viscosity control agent, pigment dispersingagent, anti-foaming agent, antifreezing agent, film forming auxiliary,ultraviolet ray absorbing agent, antioxidant, water-soluble melamine,aqueous dispersable isocyanate, etc. in a range not loweringtransparency.

Also as case demands, an emulsion of a urethane resin, acrylic siliconeresin or acrylic resin can be blended. There is a case where blending ofthose resin emulsions further improves adhesion to a substrate.

For example, to 100 parts by weight of an aqueous dispersion offluorine-containing resin may be added 0 to 50 parts by weight of a filmforming auxiliary such as a condensation derivative of ethylene glycol,propylene glycol, aliphatic ester, or a ketone solvent, and further 0 to5 parts by weight of a benzophenone type, benzotriazole type, anilideoxalate type, cyano acrylate type or triazine type ultraviolet rayabsorbing agent as it is or in the form of being dissolved in an organicsolvent such as a film forming auxiliary and 0 to 2 parts by weight of aviscosity control agent. Further if necessary, an aqueous pigmentsdispersion, organo silicate, colloidal silica or water-soluble silicatemay be added with stirring. Organo silicate is added as it is or ifnecessary, in the form of an aqueous dispersion by using a knownemulsifying agent, and a phosphoric acid salt is added in the form ofaqueous solution or aqueous dispersion. With respect to colloidal silicaor water-soluble silicate, a commercially available one is added as itis or in the form of being diluted with water. Also one or more of themcan be added simultaneously, and further as case demands, anantioxidant, etc. may be added in the form of being dissolved in anorganic solvent such as a film forming auxiliary, and then stirred formixing.

The obtained composition has a form applicable as a coating. Forexample, the composition is applied to a synthetic resin substrate byspray coating, flow coating, dip coating, etc. and dried at atemperature of from room temperature to 200° C., and thus a coatedarticle having a surface protective coating layer can be obtained.Examples of the synthetic resin substrate, on which the surfaceprotective coating layer is formed, are general-purpose resins such asvinyl chloride resin, vinyl acetate resin, styrene resin and acrylicresin; engineering plastics such as nylon, polyacetal, polycarbonate(PC), modified polyphenylene oxide (modified PPO), polyethyleneterephthalate (PET), polybutylene terephthalate (PBT), polymethylpentene (TPX), polysulfone, polyether sulfone (PES), polyphenylenesulfide (PPS), polyalylate, polyamide imide (PAI), polyether imide(PEI), polyether ether ketone (PEEK) and polyimide; and the like.

Among them, as the resin which can make the best use of the feature ofthe present invention, there are a vinyl chloride resin, acrylic resin,styrene resin, nylon, polycarbonate (PC), modified polyphenylene oxide(modified PPO), polysulfone, polyether sulfone (PES), and the like whichare easily attacked by a polar solvent. Further a more preferable effectcan be obtained in case of an acrylic resin, styrene resin,polycarbonate (PC), polysulfone and polyether sulfone (PES) which easilyaccumulate an internal stress and easily causes solvent cracking due toa solvent. Also from the viewpoint of transparency, an acrylic resin,styrene resin, polycarbonate and vinyl chloride resin are preferred.

In the present invention, a synthetic resin substrate includes thoseobtained by processing a starting synthetic resin into a desired form offilm, plate, fiber or the like through known method such as injectionmolding, melt molding, extrusion molding, blow molding, compressionmolding, solution casting or emulsion casting.

The preferred combinations of components in the aqueous dispersion ofthe present invention are then raised below. The present invention isnot limited to those combinations. “Part” represents a part by weight.

(1) (A) Aqueous dispersion of fluorine-containing 100 parts resinFluorine-containing resin: VdF copolymer/acrylic polymer composite resincontaining 1 to 30% by mole of epoxy Concentration: 50% (B) Additives 0to 10 parts Kind: Film forming auxiliary, viscosity control agent,anti-foaming agent, ultraviolet ray absorbing agent and antioxidant (C)Substrate: Polycarbonate

In this combination, a transparent resin laminated article beingexcellent in weather resistance and chemical resistance and useful forsun roof, fence, windshield hood, goggles, etc. can be obtained.

(2) (A) Aqueous dispersion of fluorine-containing 100 parts resinFluorine-containing resin: VdF/acrylic polymer composite resincontaining 1 to 10% by mole of hydroxyl Concentration: 50% (B) Additives0 to 10 parts Kind: Film forming auxiliary, viscosity control agent,anti-foaming agent, ultraviolet ray absorbing agent and antioxidant (C)Substrate: Polycarbonate

In this combination, a transparent resin laminated article beingexcellent in weather resistance and chemical resistance and useful forsun roof, fence, windshield hood, goggles, etc. can be obtained.

(3) (A) Aqueous dispersion of fluorine-containing 100 parts resinFluorine-containing resin: VdF copolymer/acrylic polymer composite resinConcentration: 50% (B) Additives 0 to 10 parts Kind: Urethane resinemulsion, film forming auxiliary, viscosity control agent, anti-foamingagent, ultraviolet ray absorbing agent and antioxidant (C) Substrate:Vinyl chloride resin

In this combination, a transparent resin laminated article beingexcellent in weather resistance and chemical resistance and useful forfilm for agriculture, net for construction, etc. can be obtained.

An acrylic resin, styrene resin, polycarbonate, vinyl chloride resin,polysulfone, polyether sulfone, etc. coated with the obtained aqueousdispersion of fluorine-containing resin are preferably used forapplications requiring mainly transparency and weather resistance suchas members for civil engineering and construction for outdoor use (forexample, sound-insulating fence for road, house wall, balcony panel, sunroof, roof members, illumination fittings, exterior wall of green house,film for agriculture, net for construction, etc.), members for car (forexample, windshield hood for motorcycle, protection cover for lamps andparts around panel), goggles, traffic signal, protection cover foradvertising panel, liquid crystal panel cover, optical fiber, solarbattery panel cover, information system-related disc, etc.

The present invention is then explained by means of preparation examplesand examples, but is not limited to them.

PREPARATION EXAMPLE 1

A 200 ml stainless steel autoclave equipped with a stirrer was chargedwith 8.8 g of cyclohexyl vinyl ether (CHVE), 8.8 g of hydroxybutyl vinylether (HBVE), 4.0 g of macromonomer (PKA5003 available from NOFCorporation) having a hydrophilic moiety, 10.0 g of ethyl vinyl ether(EVE), 66.0 g of ion-exchanged water, 0.35 g of ammoniumperfluorooctanoate (emulsifying agent), 0.35 g of potassium carbonate,0.02 g of sodium hydrogen sulfite and 0.08 g of ammonium persulfate(initiator), followed by cooling with ice, increasing the insidepressure of the autoclave to 3.5 kg/cm² with pressurized nitrogen gasand deaerating. After the pressurizing and deaerating were repeated twotimes, deaeration up to 10 mmHg was carried out and dissolved oxygen wasremoved. Then 33.5 g of chlorotrifluoroethylene (CTFE) was added andreaction was carried out at 30° C. for 12 hours to give the aqueousdispersion of Preparation Example 1 containing particles of thefluorine-containing copolymer (2). A calculated content (concentrationof functional group) of a hydroxyl-containing monomer in the resin was26.8% by mole. A solid content of the obtained aqueous dispersion was48% and an average particle size was 189 nm.

The aqueous dispersion was dried for one hour in a vacuum dryer of 150°C. The solid content was represented by a percentage of a weight of theaqueous dispersion after drying to a weight of the aqueous dispersionbefore drying.

The average particle size was measured with a laser beam scatteringparticle size analyzer (ELS-3000 available from Otsuka Denshi KabushikiKaisha).

Also the concentration of the functional group was calculated by usingcomposition of the obtained polymer.

PREPARATION EXAMPLE 2 Synthesis of Aqueous Dispersion of VdF Copolymer

A 1-liter pressure resistant reaction vessel equipped with a stirrer wascharged with 500 ml of deionized water, 0.5 g of ammoniumperfluorooctanoate and 0.05 g of nonionic emulsifying agent (MYS40available from Nikko Chemicals Co., Ltd.). After repeating feeding ofpressurized nitrogen and deaerating and then removing dissolved oxygen,the inside pressure of the vessel was increased up to 10 kgf/cm² at 60°C. with a monomer mixture comprising vinylidene fluoride(VdF)/tetrafluoroethylene (TFE)/chlorotrifluoroethylene (CTFE) in amolar ratio of 74/14/12. Then 0.2 g of ammonium persulfate was added andthe monomer mixture comprising VdF/TFE/CTFE in a molar ratio of 74/14/12was supplied continuously so that the inside pressure became constant at10 kgf/cm². After the 40-hour reaction, the inside of the vessel wasrendered to normal temperature and normal pressure to terminate thereaction. A pH of the aqueous dispersion was adjusted to 6.5 with 5%sodium hydrogencarbonate. A solid content of the obtained aqueousdispersion of fluorine-containing copolymer (1) was 42% and an averageparticle size was 126 nm.

Seed Polymerization of Acrylic Monomer

A 200 ml four-necked flask equipped with a stirrer, cooling tube andthermometer was charged with 100 g of the aqueous dispersion offluorine-containing copolymer (1), and thereto was added 1.5 g of areactive emulsifying agent (JS2 available from Sanyo Kasei KogyoKabushiki Kaisha). Heating was carried out in water bath with stirringand after the bath temperature reached 75° C., an emulsion prepared byemulsifying a mixture comprising 17 g of methyl methacrylate (MMA), 3.0g of hydroxyethyl methacrylate and 1.7 g of methoxypolyethylene glycolmethacrylate (RMA450M available from Nippon Nyukazai Kabushiki Kaisha)with 10 g of a 1% aqueous solution of reactive emulsifying agent JS2 wasadded dropwise over one hour. Immediately after that, 1 ml of a 10%solution of potassium persulfate was added to initiate a reaction. Threehours after initiating of the reaction, the bath temperature waselevated to 85° C. and held for one hour, followed by cooling. After pHof the mixture was adjusted to 7 with aqueous ammonium, filtration wascarried out with a 300 mesh metal net to give, as a filtrate, a bluishwhite aqueous dispersion of fluorine-containing composite resin (3). Asolid content of the aqueous dispersion was 45.3%, and an averageparticle size was 162 nm.

PREPARATION EXAMPLES 3 TO 5

An aqueous dispersion of Preparation Examples 3 to 5 was prepared in thesame manner as in Preparation Example 2 except that acrylic monomers forseed polymerization were changed as shown in Table 1. Characteristicsthereof are shown in Table 1.

Abbreviations in Table 1 represent the following compounds.

VdF: Vinylidene fluoride

TFE: Tetrafluoroethylene

CTFE: Chlorotrifluoroethylene

CHVE: Cyclohexyl vinyl ether

HBVE: Hydroxybutyl vinyl ether

EVE: Ethyl vinyl ether

PKA5003: Macromonomer available from NOF Corporation (Polyoxyethyleneallyl ether)

MMA: Methyl methacrylate

BA: Butyl acrylate

HEMA: Hydroxyethyl methacrylate

GMA: Glycidyl methacrylate

AAc: Acrylic acid

TABLE 1 Preparation Example 1 2 3 4 5 Components of fluorine- containingresin (g) Fluorine-containing polymer VdF — 62.8 62.8 62.8 62.8 TFE —18.6 18.6 18.6 18.6 CTFE 33.5 18.6 18.6 18.6 18.6 Other monomer CHVE 8.8— — — — HBVE 8.8 — — — — EVE 10.0 — — — — PKA5003 4.0 — — — — Monomerfor seed polymerization (based on 100 g of seed particles) MMA — 17 2024 24 BA — — 6 4 3 HEMA — 3 — — — GMA — — 38 — — AAc — — 2 — 1 RMA450M —1.7 2.4 2.0 2.0 Amount of functional groups of 26.8 3 27 0 2fluorine-containing resin (% by mole) Aqueous dispersion Solid content(% by weight) 48 45.3 48.5 45.4 45.3 Average particle size (nm) 189 162189 164 163

EXAMPLE 1

To the aqueous dispersion of fluorine-containing resin compositionobtained in Preparation Example 1 was added 10% by weight of diethyladipate solution of ultraviolet ray absorbing agent Tinuvin 1130(available from Ciba Geigy Co., Ltd.), followed by stirring so that itsamount became 20% by weight based on a solid content of the resin.Further to the aqueous dispersion were added 0.1% by weight of FS013B(available from Dow Corning Co., Ltd.) as an anti-foaming agent and 1.0%by weight of 10 wt % aqueous solution of Adekanol UH420 (available fromAsahi Denka Kabushiki Kaisha) as a thickener, followed by stirring at400 rpm for one hour to give a clear coating. The coating was appliedand extended on a polycarbonate plate (available from Nippon Test PanelKabushiki Kaisha) with a 10 mil doctor blade, and dried at roomtemperature for one hour and further dried at 120° C. for 20 minutes.The following tests were carried out by using the obtained test plate.The results are shown in Table 2.

Appearance: Appearance of the dried film was judged with naked eyes withrespect to transparency, coloring and cracking of a substrate.

Adhesion: A cross-cut adhesion test was carried out by cutting the filmsurface into 25 squares of 2 mm. Figures in the table show the number ofsquares which remained after the adhesion test.

Hot water resistance test: After dipping the test plate in hot water of80° C. for two hours, its appearance and adhesion were evaluated.

Weather resistance: A 200-hour accelerated weather resistance test wascarried out with I-Super UV tester (available from Iwasaki DenkiKabushiki Kaisha), and appearance and color difference (ΔE) weredetermined. A color-difference meter available from Suga ShikenkiKabushiki Kaisha was used.

EXAMPLES 2 TO 8

Test plates were produced in the same manner as in Example 1 except thatan aqueous dispersion of fluorine-containing resin composition and asubstrate were changed as shown in Table 2. The tests were carried outin the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 1

An accelerated weather resistance test was carried out by using anon-coated polycarbonate plate. The results are shown in Table 2.

Comparative Example 2

A solvent lacquer type coating varnish Zeffle LC930 (available fromDAIKIN INDUSTRIES, LTD.) of fluorine-containing resin as a solvent-basedcoating was applied and extended on a polycarbonate plate (availablefrom Nippon Test Panel Kabushiki Kaisha) with a 10 mil doctor blade, anddried at room temperature for one hour and a small cracking arose on thesubstrate.

TABLE 2 Aqueous dispersion of fluorine-containing Synthetic After hotwater Weather resistance resin resin Initially resistance test Color(Prep. Ex.) substrate Appearance Adhesion Appearance Adhesion Appearancedifference Ex. 1 1 PC Transparent 25/25 Transparent 25/25 Transparent15  Ex. 2 2 PC Transparent 25/25 Transparent 25/25 Transparent 2 Ex. 3 2PMMA Transparent 25/25 Transparent 25/25 Transparent 3 Ex. 4 2Polysulfone Transparent 25/25 Transparent 25/25 Transparent 5 Ex. 5 2PES Transparent 25/25 Transparent 25/25 Transparent 5 Ex. 6 3 PSTransparent 25/25 Transparent 25/25 Transparent 4 Ex. 7 5 PC Transparent25/25 Transparent 19/25 Transparent 4 Ex. 8 4 PC Transparent 25/25Transparent 15/25 Transparent 2 Com. — PC Transparent — — — Turned 31 Ex. 1 yellow Com. Solvent type PC Cracking — — — — — Ex. 2 PC:Polycarbonate PMMA: Polymethyl methacrylate PES: Polyether sulfone PS:Polystyrene

INDUSTRIAL APPLICABILITY

According to the present invention, a surface protective coating layerof a fluorine-containing resin being excellent in weather resistance andchemical resistance can be formed safely on a synthetic resin substratewith good adhesion thereto.

What is claimed is:
 1. A method of forming a surface protective coatingon a polycarbonate substrate which comprises applying an aqueousdispersion of fluorine-containing resin having epoxy group to thepolycarbonate substrate.
 2. The method of claim 1, wherein the aqueousdispersion of fluorine-containing resin is prepared byseed-polymerizing, in an aqueous dispersion of vinylidene fluorideresin, a monomer having radically polymerizable unsaturated bond withparticles of said vinylidene fluoride resin.
 3. The method of claim 1,wherein the polycarbonate substrate is transparent.
 4. A polycarbonatelaminated article having a surface protective coating layer formed bythe method of claim
 1. 5. The method of claim 2, wherein thepolycarbonate substrate is transparent.
 6. A polycarbonate laminatedarticle having a surface protective coating layer formed by the methodof claim
 2. 7. A polycarbonate laminated article having a surfaceprotective coating layer formed by the method of claim
 3. 8. Apolycarbonate laminated article having a surface protective coatinglayer formed by the method of claim
 5. 9. The method of claim 1, whichcomprises applying the aqueous dispersion of fluorine-containing resinhaving epoxy group directly to the polycarbonate substrate.